Major Depression & Bipolar Disorder
Board review of unipolar (MDD, persistent depressive disorder) vs bipolar-spectrum mood disorders, emphasizing DSM-5 symptom counts/durations, first-line pharmacotherapy, and the next-best-step decisions boards test. Centered on the pivotal question of any prior manic/hypomanic episode, which reclassifies the illness and reshapes management. Reviewed for accuracy: DSM-5 criteria, drug pitfalls, and serotonin-syndrome/NMS contrast confirmed correct; the one substantive fix was Vignette 1's manic-episode duration (6 days corrected to an unambiguous 8 days ≥1 week to secure the Bipolar I diagnosis).
The unipolar vs bipolar divide
Mood disorders split into two families that boards test relentlessly: unipolar depression (major depressive disorder, persistent depressive disorder) versus the bipolar spectrum (bipolar I, bipolar II, cyclothymia). The single most important question in any depressed patient is whether they have ever had a manic or hypomanic episode — because that one fact reclassifies the illness as bipolar and completely changes treatment (a lone antidepressant can flip a bipolar patient into mania).
Every episode is defined by a symptom count sustained over a minimum duration, so the exam rewards knowing the numbers cold: 2 weeks for a major depressive episode, 1 week for mania, 4 days for hypomania, and 2 years for the chronic low-grade disorders. Diagnosis additionally requires functional impairment and exclusion of a substance or medical cause — every depressed vignette should prompt you to consider hypothyroidism, anemia, and substance use before committing to a primary mood disorder.
- Major depressive episode: ≥5 of 9 symptoms for ≥2 weeks; at least one must be depressed mood or anhedonia; must cause distress/impairment.
- Persistent depressive disorder (dysthymia): depressed mood most days for ≥2 years (≥1 yr in children) + ≥2 associated symptoms; never symptom-free >2 months.
- Manic episode: elevated/expansive/irritable mood plus increased energy/activity ≥1 week (or any duration if hospitalization is needed) + ≥3 symptoms (≥4 if mood only irritable); marked impairment, psychosis, or hospitalization → Bipolar I.
- Hypomanic episode: same symptoms ≥4 days, an observable change but no marked impairment, no psychosis, no hospitalization; hypomania + a past major depressive episode = Bipolar II.
- Cyclothymia: ≥2 years of subthreshold hypomanic and depressive symptoms.
- Epidemiology: MDD lifetime ~12–17%, women 2× men; Bipolar I ~1%, roughly equal by sex, earlier onset (late teens–20s), strongly heritable.
SIGECAPS — major depression (need ≥5, one being depressed mood or anhedonia):
- Sleep (insomnia or hypersomnia)
- Interest ↓ (anhedonia)
- Guilt / worthlessness
- Energy ↓ (fatigue)
- Concentration ↓
- Appetite / weight change
- Psychomotor agitation or retardation
- Suicidality
DIGFAST — mania (need ≥3, or ≥4 if mood only irritable):
- Distractibility
- Indiscretion / impulsivity (risky spending, sex)
- Grandiosity
- Flight of ideas
- Activity (goal-directed) ↑
- Sleep need ↓
- Talkativeness / pressured speech
Key contrast: manic sleep is a decreased need for sleep (feels rested after 3 hours) — distinct from depressive insomnia (wants to sleep but can't).
Mood disorders — criteria & timeframes
| Disorder | Core requirement | Min duration |
|---|---|---|
| Major depressive episode | ≥5/9 sx incl. depressed mood or anhedonia | 2 weeks |
| Persistent depressive disorder | Depressed mood + ≥2 associated sx | 2 years (1 yr kids) |
| Manic episode (→ Bipolar I) | Elevated/irritable mood + ↑energy + ≥3 DIGFAST; marked impairment / psychosis / hospitalization | 1 week (or any if hospitalized) |
| Hypomanic episode (→ Bipolar II) | Same sx, observable but no marked impairment/psychosis | 4 days |
| Cyclothymia | Subthreshold hypomanic + depressive sx | 2 years (1 yr kids) |
| Bipolar I vs II | I = ever manic; II = hypomania + past MDE, never manic | — |
- MDD first-line: an SSRI (sertraline, escitalopram, fluoxetine, citalopram) ± psychotherapy (CBT/IPT); combination is best for moderate–severe disease. SNRIs (venlafaxine, duloxetine) are alternatives.
- Antidepressants take 4–6 weeks to work; after remission continue ≥6 months (continuation phase) to prevent relapse.
- Inadequate response after an adequate trial (≥6–8 wk at therapeutic dose) → optimize dose, then switch or augment.
- Acute bipolar mania: mood stabilizer (lithium or valproate) and/or an atypical antipsychotic; severe → combine.
- Bipolar depression: quetiapine, lurasidone, lamotrigine, or lithium — never an antidepressant alone.
- Bipolar maintenance: lithium first-line — the agent best proven to reduce suicide.
- ECT = fastest and most effective; use for psychotic, catatonic, pregnant, food-refusing, or acutely suicidal/refractory depression.
- NEXT BEST STEP: before prescribing any antidepressant, screen for prior mania/hypomania (unmask bipolar); a patient with an active suicidal plan → ensure safety / hospitalize first.
Drug comparison — uses & pitfalls
| Drug | Use | Key adverse effect / monitor |
|---|---|---|
| SSRIs | MDD, anxiety (1st-line) | Sexual dysfunction, GI upset, hyponatremia (SIADH), serotonin syndrome; black-box suicidality <25 yo |
| Bupropion | MDD, smoking cessation; no sexual SE | Lowers seizure threshold — avoid in eating disorders / seizure |
| Mirtazapine | MDD with insomnia + poor appetite | Weight gain, sedation |
| Lithium | Bipolar maintenance (↓ suicide) | Narrow index; nephrogenic DI, hypothyroidism, tremor, Ebstein anomaly (teratogen); monitor renal/thyroid/levels |
| Valproate | Acute mania, mixed / rapid cycling | Hepatotoxicity, pancreatitis, neural-tube defects, thrombocytopenia |
| Lamotrigine | Bipolar depression & maintenance | Stevens–Johnson syndrome — titrate slowly |
Vignette 1. A 21-year-old man is brought in after 8 days of barely sleeping, rapid pressured speech, grandiose plans to "launch three startups," and a reckless-driving arrest.
- Dx: manic episode → Bipolar I (≥1 wk and marked impairment/need for hospitalization → mania, not hypomania). Next step: atypical antipsychotic ± mood stabilizer; rule out stimulant use.
Vignette 2. A 30-year-old woman has 3 weeks of low mood, anhedonia, insomnia, guilt, and weight loss.
- Before starting an SSRI: ask about past periods of decreased need for sleep with elevated activity — you must exclude bipolar to avoid precipitating mania. Also check TSH.
Vignette 3. A widow 3 weeks after her husband's death cries in waves, longs for him, but keeps her self-esteem intact and denies active suicidal intent.
- Dx: normal grief, not MDD → supportive reassurance, not antidepressants (DSM-5 removed the bereavement exclusion, so a full MDE during grief can still be MDD).
- Serotonin syndrome: hyperthermia, clonus/hyperreflexia, autonomic instability, agitation — from SSRI + MAOI / triptan / tramadol / linezolid / MDMA. Tx: stop drug, supportive care, cyproheptadine. (Contrast NMS: lead-pipe rigidity, hyporeflexia, from antipsychotics, slower onset.)
- SSRI discontinuation syndrome: flu-like symptoms, dizziness, paresthesias — worst with paroxetine (short half-life); fluoxetine (long half-life) causes the least.
- Antidepressant-induced mania unmasks bipolar — always screen first.
- Postpartum spectrum: blues (days 2–5, resolve ≤2 wk, supportive) vs depression (onset over weeks; SSRI + therapy) vs psychosis (emergency — hospitalize).
- Grief vs MDD: grief comes in waves with preserved self-worth and passive thoughts of joining the deceased; MDD is pervasive with worthlessness and active suicidality.
- Atypical depression: mood reactivity, hypersomnia, hyperphagia, leaden paralysis, rejection sensitivity → SSRIs first-line (MAOIs classically effective).
Practice Psychiatry now
Board-style questions, spaced-repetition flashcards, and a Socratic AI tutor — free to start.